JP4948012B2 - Surface emitting laser element and method for manufacturing surface emitting laser element - Google Patents

Description

  The present invention relates to a surface emitting laser element for forming a mesa post including at least an upper reflecting mirror and a method for manufacturing the surface emitting laser element.

  In a vertical cavity surface emitting laser (VCSEL), the direction in which light resonates is perpendicular to the substrate surface, and is perpendicular to the substrate surface. Has a structure in which laser light is emitted. For this reason, the surface-emitting laser element can easily form a two-dimensional array of elements as compared with the conventional edge-emitting laser element. In addition, unlike edge-emitting laser elements, surface-emitting laser elements do not need to be cleaved to provide a mirror, and the volume of the active layer is extremely small, so that laser oscillation is possible at an extremely low threshold. There are advantages such as low electric power. Such a surface emitting laser element is used not only as a light source for communication but also as a signal light source for high-speed optical transmission in datacom communication such as gigabit Ethernet and fiber channel.

  The surface-emitting laser element has a structure in which an active layer is provided between a pair of semiconductor multilayer mirrors on a semiconductor substrate of GaAs or InP. In particular, a GaAs surface emitting laser element can constitute an AlGaAs multilayer mirror having good thermal conductivity and high reflectance, and can emit laser light in the 0.8 to 1.0 μm band. A surface emitting laser element using a GaInNAs-based material for the active layer can emit laser light in a long wavelength band of 1.2 to 1.6 μm. As such a surface emitting laser element, a current confining type surface emitting laser element is proposed in which an AlAs oxide layer is formed to confine the current injection region in order to increase the current efficiency and reduce the threshold current value. (See Patent Document 1 and Patent Document 2).

FIG. 8 is a schematic cross-sectional view illustrating the configuration of a conventional surface emitting laser element. As shown in FIG. 8, the surface emitting laser element 101 has a thickness of λ / 4n (λ is a long oscillation and n is a refractive index) in order on a substrate 102 made of n-GaAs. ) N-Al _0.9 Ga _0.1 As / n-Al _0.2 Ga _0.8 As of 35 pairs, a lower multilayer mirror 103, a lower cladding layer 105, an active layer 106 having a multiple quantum well structure, and an upper cladding layer 107 And a mesa post MP5 having a structure in which 25 pairs of p-Al _0.9 Ga _0.1 As / n-Al _0.2 Ga _0.8 As each having a thickness of λ / 4n are stacked. In addition, in one layer of the upper multilayer reflector 108 near the active layer 106, a current confinement layer 108a having a current injection region 108c located on the central axis of the mesa post MP5 and an oxide region 108b formed of an Al oxide layer. Is provided. The current confinement layer 108a also functions as an optical confinement layer for confining laser light.

  A ring-shaped p-side electrode 110 connected to the electrode pad 112 is formed on the upper multilayer reflector 108, and an n-side electrode 111 is formed on the back surface of the substrate 102. A polyimide layer 109 is disposed around the mesa post MP5. The p-side electrode 110 has an opening at the center of the upper surface portion of the mesa post MP5, and this opening functions as an emission window for outputting the laser light L generated in the active layer 106 to the outside.

  With this configuration, when a suitable voltage is applied between the p-side electrode 110 and the n-side electrode 111, the surface-emitting laser element 101 is directed upward from the central opening of the p-side electrode 110 toward the mesa post MP5, for example, A laser beam L having a wavelength of 850 nm is emitted.

US Pat. No. 5,493,577 Japanese Patent Laid-Open No. 2003-8142

By the way, in the surface-emitting laser element 101, after the upper multilayer reflector 108 is stacked, a depth reaching the layer below the semiconductor layer corresponding to the current confinement layer 108a by performing a photolithography process and an etching process. A frustoconical mesa post MP5 is formed. By forming the mesa post MP5, the end faces of the stacked semiconductor layers are exposed. Then, after forming the mesa post MP5, for example, by performing an oxidation treatment at about 400 ° C. in a water vapor atmosphere, the Al in the semiconductor layer corresponding to the current confinement layer 108a is selectively oxidized from the outside of the mesa post MP5, thereby oxidizing the region. 108b is formed. In the surface-emitting laser element 101 shown in FIG. 8, an Al _0.98 Ga _0.02 As layer having a higher Al composition ratio than the film constituting the other upper multilayer reflector 108 is used as the semiconductor layer corresponding to the current confinement layer 108a or about 30 nm. By forming the AlAs thin film layer, it is selectively oxidized and the volume shrinkage due to the conversion to the Al oxide layer is reduced.

However, in the oxidation treatment for forming the current confinement layer 108a, the end face of each semiconductor layer forming the mesa post MP5 is also exposed, so that the end face of each semiconductor layer is also exposed to strong oxidation conditions. For this reason, as shown in FIG. 9, the Al _0.9 Ga _0.1 As layer having a high Al composition, which is the lower refractive index side layer, of the upper multilayer reflector 108 is oxidized in an annular shape along the periphery of the mesa post MP5. As a result, an oxidized region 108d of about several hundreds of nanometers has been formed. Since the Al _0.9 Ga _0.1 As layer is designed to be λ / 4n with respect to the wavelength λ of the laser light, the Al _0.9 Ga _0.1 As layer is thick and has a large number of pairs. Thus, the volume shrinkage due to the conversion to the Al oxide layer cannot be completely prevented, and the stress generated by this volume shrinkage may cause a decrease in the reliability of the surface emitting laser element.

  In particular, as shown in FIG. 8, when the active layer 106 is present in the mesa post MP5 portion and the end face of the active layer is exposed on the side surface of the mesa post, the active layer is caused by the stress generated by the volume shrinkage due to the conversion to the Al oxide layer. There is a problem that defects are easily generated on the end face, and the active layer 106 itself is damaged.

  This will be specifically described with reference to FIGS. 10 and 11. 10 and 11 are schematic views for explaining dislocations generated in the active layer 106 in the mesa post MP5 of the surface emitting laser element 101 shown in FIG. It is shown as a sectional view. First, as shown in FIG. 10, a plurality of dislocations are formed in the peripheral portion of the active layer 106 due to stress caused by volume change due to oxidation of the upper multilayer reflector 108 and damage given in the etching process for forming the mesa post MP5. DL occurs.

  When energization is continued in the surface emitting laser, the dislocation DL expands and propagates depending on the carriers generated based on the absorption of spontaneous emission light guided from the light emitting region in the active layer 106. Then, as shown in FIG. 11, when the dislocation DL grown from the peripheral portion of the active layer 106 reaches the light emitting area EA, a failure of the surface emitting laser element is induced.

  As described above, there is a problem that the active layer 106 itself is damaged due to the stress caused by the volume shrinkage of the upper multilayer reflector 108 due to oxidation, causing a failure in the surface emitting laser element.

  The present invention has been made in view of the above, and in a surface-emitting laser element in which a mesa post including an active layer is formed, a highly reliable surface-emitting laser element and surface-emitting laser element with reduced damage to the active layer It aims at providing the manufacturing method of.

  In order to solve the above-described problems and achieve the object, a surface emitting laser device according to the present invention includes an active layer formed on a substrate and a current supplied to the active layer by confining an externally injected current. A constriction layer, a lower reflective layer formed between the substrate and the active layer, and an upper reflector formed on the active layer, and a groove surrounding a light emitting region in the active layer is provided In the surface emitting laser element in which the mesa post including at least the upper reflecting mirror is formed, a cross section having a depth reaching the semiconductor layer corresponding to the current confinement layer is formed outside the groove.

  In the surface-emitting laser element according to the present invention, the cross section is formed before the groove is provided.

  Further, in the surface emitting laser element according to the present invention, in the current confinement layer, a partial region of the semiconductor layer corresponding to the current confinement layer is oxidized through the cross section in the oxidation treatment after the cross section is formed. It is characterized by being formed by.

  In the surface emitting laser element according to the present invention, the groove is formed after the oxidation treatment is performed.

  In the surface emitting laser element according to the present invention, the cross section is formed by providing a hole having a depth reaching the semiconductor layer corresponding to the current confinement layer.

  The surface emitting laser element according to the present invention is characterized in that a plurality of the holes are provided on concentric circles.

  In the surface emitting laser element according to the present invention, the cross section is formed by providing another groove having a depth reaching the semiconductor layer corresponding to the current confinement layer.

  Further, in the surface emitting laser element according to the present invention, the groove has a depth for dividing the active layer.

  In the surface emitting laser element according to the present invention, the semiconductor layer corresponding to the current confinement layer includes a predetermined semiconductor layer in the upper reflecting mirror, a predetermined semiconductor layer adjacent to the upper reflecting mirror, and the lower reflecting mirror. And a predetermined semiconductor layer adjacent to the lower reflecting mirror.

  The surface emitting laser element according to the present invention is characterized in that the upper reflecting mirror and the lower reflecting mirror include an AlGaAs-based semiconductor layer.

  Also, the method of manufacturing the surface emitting laser device according to the present invention includes a stacking step in which a semiconductor layer is formed by stacking a lower reflective layer, an active layer, a semiconductor layer corresponding to a current confinement layer, and an upper reflector on a substrate. And a cross-section forming step for forming a cross section having a depth reaching the semiconductor layer corresponding to the current confinement layer, and a partial region of the semiconductor layer corresponding to the current confinement layer via the cross section. And a mesa post forming step of forming a mesa post including at least the upper reflector by providing a groove surrounding the light emitting region in the active layer inside the cross section after the oxidation step. And

  According to the surface-emitting laser element and the method for manufacturing the surface-emitting laser element according to the present invention, the cross-section having a depth reaching the semiconductor layer corresponding to the current confinement layer is formed outside the groove for forming the mesa post and the oxidation treatment is performed. Thus, a highly reliable surface-emitting laser element with reduced damage to the active layer can be realized.

  Hereinafter, a surface emitting laser element and a method for manufacturing the surface emitting laser element according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments. In the description of the drawings, the same parts are denoted by the same reference numerals. Further, the drawings are schematic, and it should be noted that the relationship between the thickness and width of each layer, the ratio of each layer, and the like are different from the actual ones. Also in the drawings, there are included portions having different dimensional relationships and ratios.

(Embodiment 1)
First, the surface emitting laser element according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the configuration of the surface emitting laser element according to the first embodiment. As shown in FIG. 1, a surface emitting laser element 1 according to a first embodiment includes, in order, a lower multilayer reflector 3, a lower cladding layer 5, and a multiple quantum well structure on a substrate 2 made of p-GaAs. The active layer 6, the upper cladding layer 7, and the upper multilayer mirror 8 are stacked. In this surface-emitting laser element 1, by providing an annular groove 21 that surrounds the light emitting region in the active layer 6, a truncated conical mesa post MP <b> 1 including the upper laminated portion from the upper end portion of the lower multilayer reflector 3 is formed. Has been. Further, in the surface emitting laser element 1, an annular groove 22 that is separate from the annular groove 21 is formed outside the annular groove 21.

The lower multilayer mirror 3 is formed as a distributed reflection reflector (DBR) and has a structure in which, for example, 35 pairs of p-Al _0.9 Ga _0.1 As / p-Al _0.2 Ga _0.8 As are stacked. Have. The upper multilayer mirror 8 is formed as a distributed reflector, and has a structure in which, for example, 25 pairs of n-Al _0.9 Ga _0.1 As / n-Al _0.2 Ga _0.8 As are stacked. The thickness of each semiconductor layer forming the lower multilayer reflector 3 and the upper multilayer reflector 8 is λ / 4n (λ: oscillation wavelength, n: refractive index).

  A current confinement layer 3a having a current injection region 3c on the central axis of the mesa post MP1 is formed on the upper layer of the lower multilayer mirror 3. The current confinement layer 3a is formed by laminating an AlAs layer on the upper end of the lower multilayer reflector 3 and oxidizing a partial region of the AlAs layer through the annular groove 22 in the oxidation process after the formation of the annular groove 22. The Therefore, in the current confinement layer 3a, the non-oxidized central non-oxidized AlAs layer constitutes the current injection region 3c as an opening, and the outside of the current injection region 3c from the outer periphery of the opening is an oxidation region having an insulating property due to oxidation 3b is comprised. The current confinement layer 3a constricts the current injected from the p-side electrode 11 to increase the current density in the active layer 6. The oxidized region 3b has a function of controlling the oscillation transverse mode as an optical confinement layer because the outer side from the outer periphery of the opening has a refractive index different from that inside the opening due to oxidation. In FIG. 1, the AlAs layer corresponding to the current confinement layer 3a is not only the upper end of the lower multilayer reflector 3, but also the side near the active layer 6 in the lower multilayer reflector 3, or the lower multilayer reflector. 3 may be formed adjacent to 3.

The lower cladding layer 5 and the upper cladding layer 7 are stacked so as to sandwich the active layer 6 from above and below, and form an optical resonator together with the active layer 5. The lower cladding layer 5 is made of, for example, p-Al _0.3 Ga _0.7 As, and the upper cladding layer 7 is made of, for example, n-Al _0.3 Ga _0.7 As. The lower clad layer 5 and the upper clad layer 7 have optical lengths substantially equal to each other so that the antinodes of the standing waves generated in the optical resonator come to the center of the active layer 6 in the layer thickness direction. It is preferable to have a film thickness.

The active layer 6 has a multiple quantum well (MQW) structure made of, for example, GaAs / Al _0.2 Ga _0.8 As. The active layer 6 is injected from the p-side electrode 11 and emits light according to the current confined by the current confinement layer 3a. Spontaneously emitted light emitted from the light emitting region of the active layer 6 is amplified by an optical resonator formed by the lower cladding layer 5 and the upper cladding layer 7 and emitted as laser light L from the upper surface of the upper multilayer mirror 8. Is done.

  An n-side electrode 10 connected to the electrode pad 12 is formed on the upper multilayer mirror 8 and a p-side electrode 11 is formed on the back surface of the substrate 2 facing the n-side electrode 10. The n-side electrode 10 has an opening as an emission window for emitting the laser light L to the outside at the center of the upper surface portion of the mesa post MP1. Further, an insulating layer 9 formed of a SiN film is formed around the mesa post MP1.

  Next, the annular grooves 21 and 22 formed in the surface emitting laser element 1 will be described with reference to FIG. FIG. 2 is a diagram for explaining the positions of the annular grooves 21 and 22 when the surface emitting laser element 1 is viewed from above. In the surface emitting laser element 1, a truncated conical mesa post MP 1 is formed by providing the annular groove 21. The bottom of the annular groove 21 reaches the lower cladding layer 5, and the annular groove 21 has a depth that divides the active layer 6. The annular groove 21 surrounds the light emitting region in the active layer 6 and has an inner diameter that can sufficiently surround the oxidized region 3c. For example, the depth of the annular groove 21 is about 5 μm, and the inner diameter of the annular groove 21 is about 30 μm. Note that the mesa post MP1 has a substantially truncated cone shape due to the influence of the etching process in forming the annular groove 21.

  In the surface emitting laser element 1, as shown in FIG. 2, an annular groove 22 is further formed outside the annular groove 21 forming the mesa post MP1. The annular groove 22 has a depth reaching the AlAs layer corresponding to the current confinement layer 3a. For example, the inner diameter of the annular groove 22 is about 50 μm, and the groove width of the annular groove 22 is about 10 μm. The annular groove 22 is formed before the annular groove 21 is formed. Then, after the annular groove 22 is formed, an oxidation process for oxidizing the AlAs layer corresponding to the current confinement layer 3a is performed, and the annular groove 21 is formed after this oxidation process. The region sandwiched between the annular groove 21 and the annular groove 22 becomes an annular shape having a substantially trapezoidal cross-sectional shape whose width becomes narrower upward due to the influence of the etching process for forming the annular groove 21 and the annular groove 22. Yes.

  Next, a method for manufacturing the surface emitting laser element 1 shown in FIG. 1 will be described. 3A to 3E are diagrams for explaining a method of manufacturing the surface emitting laser element 1 shown in FIG. First, as shown in FIG. 3A, the lower multilayer reflector 3, the lower clad layer 5, the active layer 6, the upper clad layer 7, and the upper multilayer reflector 8 are laminated on the substrate 2 by epi growth. A semiconductor laminate is formed. Note that an AlAs layer 3d corresponding to the current confinement layer 3a is laminated on the uppermost layer of the lower multilayer reflector 3.

  Next, as shown in FIG. 3-2, an annular groove 22 is formed by performing a photolithography process and an etching process. In the etching process, processing conditions are set so that the depth of the annular groove 22 reaches at least a part of the AlAs layer 3d corresponding to the current confinement layer 3a. Further, it is desirable that the annular groove 22 has a depth reaching a layer located under the AlAs layer so that the AlAs layer 3d corresponding to the current confinement layer 3a is sufficiently exposed. By forming the annular groove 22, a cross section having a depth reaching the AlAs layer 3d and exposing the end face of the AlAs layer 3d is formed.

  Next, oxidation treatment is performed at a temperature of about 400 ° C. in a steam atmosphere. As a result, as shown in FIG. 3C, the AlAs layer 3d is gradually oxidized from the end face exposed by forming the annular groove 22, and the oxidized region 3b and the non-oxidized region corresponding to the current injection region 3c Selectively oxidized.

  Next, as shown in FIG. 3-4, by performing a photolithography process and an etching process, the annular groove 22 is positioned so that the non-oxidized region corresponding to the current injection region 3c is located substantially in the center of the annular groove 22. 21 is provided to form the mesa post MP1. Next, as shown in FIG. 3-5, after the SiN film is stacked, the insulating layer 9 is formed by removing the SiN film in the region corresponding to the n-side electrode 10, and then the ring-shaped n-side electrode 10 is formed. Form. Then, the back surface of the substrate 2 is appropriately polished and the thickness of the substrate 2 is adjusted to, for example, 200 μm, and then the p-side electrode 11 is formed on the back surface of the substrate 2. Then, the surface emitting laser element 1 is manufactured by forming the electrode pad 12 for connecting with an external terminal with a wire so that it may contact with the ring-shaped n-side electrode 10.

  As described above, in the surface-emitting laser device 1 according to the first embodiment, before forming the annular groove 21 for forming the mesa post MP1, an AlAs layer corresponding to at least the current confinement layer 3a is formed outside the annular groove 21. After forming the annular groove 22 having a cross section with a depth reaching 3d, an oxidation treatment is performed to form the current confinement layer 3a. In other words, the surface emitting laser element 1 is provided with the step of forming the mesa post MP1 after forming the annular groove 22 and performing the oxidation treatment to form the current confinement layer 3a. As described above, the surface emitting laser element 1 forms the annular groove 21 after the oxidation treatment even when the end face region of the layer corresponding to the active layer 6 is damaged by the stress caused by the volume change due to the oxidation treatment. Then, the mesa post MP1 in which the continuity between the damaged region and the active layer 6 in the mesa post MP1 is cut off is formed. As a result, the surface emitting laser element 1 can reduce the influence received from the damaged region, and can reduce the damage to the active layer 6 due to the oxidation treatment. Similarly, the upper layer of each layer corresponding to the lower multilayer reflector 3, the layer corresponding to the lower clad layer 5, the layer corresponding to the upper clad layer 7, and the upper multilayer reflector 8 due to the stress caused by the volume change due to oxidation treatment. Even when the end face region of each layer corresponding to the above is damaged, the mesa post MP1 that is disconnected from the damaged region can be formed by forming the annular groove 21 after the oxidation treatment. As a result, according to the first embodiment, it is possible to realize a highly reliable surface emitting laser element in which damage to each layer due to oxidation treatment is reduced.

  The oxidation width in the oxidation treatment of the lower multilayer semiconductor layer 3 and the upper multilayer semiconductor layer 8 is in the range of several hundred nm to several μm from the exposed surface in the cross section of the annular groove 22. In order to separate the oxidized regions in the lower multilayer semiconductor layer 3 and the upper multilayer semiconductor layer 8 from the mesa post MP1, the annular groove 21 is formed so that the mesa post MP1 is formed at least 5 μm inside the inner periphery of the annular groove 22. It is preferable to form.

  The annular groove 21 is formed using an ion plasma etching method, a wet etching method, or the like. Here, there may be a difference between the etching rate of the oxidized region and the etching rate of the non-oxidized region in the oxidation treatment for forming the current confinement layer 3a. For this reason, in order to avoid a shape abnormality due to the difference in etching rate, it is preferable to perform etching while avoiding the region near the cross section exposed during the oxidation step. In other words, the annular groove 21 is preferably disposed sufficiently inside the annular groove 22. As a result, the annular groove 21 having a normal shape can be stably formed, and the shape of the mesa post MP1 can be made substantially frustoconical. Therefore, the insulation failure caused by the stacking failure of the insulating layer 9 due to the shape abnormality of the mesa post MP1. In addition, it is possible to manufacture a surface emitting laser element exhibiting high reliability in which contact failure due to shape failure of the n-side electrode 10 is prevented.

  In the first embodiment, the case where the annular annular groove 21 shown in FIG. 2 is formed has been described. However, the annular groove 21 for forming the mesa post MP1 isolates the damaged region from the oxidation from the mesa post MP1 region. For example, a rectangular annular groove 21a as shown in FIG. 4 may be used. In this case, the annular groove 22 for forming the current confinement layer 3a only needs to be separated from the annular groove 21a by a sufficient distance. For example, the annular groove 22a shown in FIG. 4 may be used. Further, the annular groove 21 for forming the mesa post MP1 does not necessarily need to be annular, and any shape that separates the oxidized region and the mesa post MP1 region is sufficient.

  Further, it is sufficient for the annular groove 21 to have at least a depth for dividing the active layer 6. By setting the annular groove 21 to a depth that at least divides the active layer 6, it is possible to prevent the transition starting from the active layer end face damaged during the oxidation treatment from reaching the light emitting region. Further, by setting the annular groove 21 to a depth reaching the active layer 6, the upper multilayer reflector 8 is isolated from the end face damaged from the oxidation process of each layer corresponding to the upper multilayer reflector 8 and the upper multilayer reflector 8. The influence of the oxidized region of each layer corresponding to the film reflecting mirror 8 on the active layer 6 can be reduced.

(Embodiment 2)
Next, a surface emitting laser element according to the second embodiment will be described. FIG. 5 is a plan view of the surface emitting laser element according to the second embodiment as viewed from above. As shown in FIG. 5, the surface-emitting laser element according to the second embodiment is located on the outer side of the annular groove 21 instead of the annular groove 22 shown in FIG. Are provided with a plurality of holes 22b. The hole 22b has a depth that reaches at least a part of the AlAs layer corresponding to the current confinement layer 3a, and forms a cross section that reaches the AlAs layer corresponding to the current confinement layer 3a. When the surface emitting laser element according to the second embodiment is cut along the line xx in FIG. 5, the surface emitting laser element has substantially the same cross-sectional structure as the surface emitting laser element 1 shown in FIG.

  Similar to the annular groove 22 in the first embodiment, the hole 22b is formed before the annular groove 21 forming the mesa post MP1 is formed, and the AlAs layer 3d corresponding to at least the current confinement layer 3a is formed outside the annular groove 21. Having a cross-section with a depth of up to In the second embodiment, as in the first embodiment, the current confinement layer 3a is formed by performing an oxidation treatment after forming the hole 22b. In other words, in the second embodiment, as in the first embodiment, after forming the hole 22b and performing the oxidation treatment to form the current confinement layer 3a, the annular groove 21 is formed to form the mesa post.

  The AlAs layer 3d corresponding to the current confinement layer 3a may have a difference in oxidation rate in the oxidation process depending on the crystal structure. In this case, after providing the holes 22b corresponding to the crystal plane orientation with a slow oxidation rate, the current injection region 3c, which is a substantially circular non-oxidized region, is formed in the center by diffusing water vapor and advancing the oxidation. be able to. The shape of the holes 22b, the number of the holes 22b, and the arrangement of the holes 22b may be set according to the oxidation conditions.

  As described above, according to the second embodiment, similarly to the surface emitting laser element according to the first embodiment, it is possible to realize a highly reliable surface emitting laser element in which damage to each layer due to oxidation treatment is reduced. it can.

  In addition, after performing the process similar to the lamination | stacking process shown to FIGS. 3-1, the hole 22b is formed by performing a photolithography process and an etching process, and it is the same as each process shown to FIGS. 3-3 to 3-5 Thus, the surface emitting laser element according to the second embodiment is manufactured.

(Embodiment 3)
Next, a third embodiment will be described. FIG. 6 is a cross-sectional view showing the configuration of the surface emitting laser element according to the third embodiment. As shown in FIG. 6, the surface emitting laser element 31 according to the third embodiment is different from the first embodiment in that n-Al _0.9 Ga _0.1 As / n-Al _0.2 Ga _0.8 is formed on a substrate 32 that is n-GaAs. A lower multilayer reflector 33 in which a plurality of pairs of As are stacked, a lower cladding layer 35 formed of n-Al _0.3 Ga _0.7 As, an upper cladding layer 37 formed of p-Al _0.3 Ga _0.7 As, p- An upper multilayer mirror 38 in which a plurality of pairs of Al _0.9 Ga _0.1 As / p-Al _0.2 Ga _0.8 As is stacked is provided. A p-side electrode 40 connected to the electrode pad 12 is formed on the upper multilayer film reflecting mirror 38, and an n-side electrode 41 is formed on the back surface of the substrate 32 facing the p-side electrode 40.

  The current confinement layer 38 a is provided, for example, in the lower end layer of the upper multilayer-film reflective mirror 38. Similar to the current confinement layer 3a in the first embodiment, the current confinement layer 38a has a current injection region 38c, which is a non-oxidized region, and an oxidation region 38b on the central axis of the mesa post MP3. Note that the AlAs layer corresponding to the current confinement layer 38a may be formed adjacent to the upper multilayer reflector 38 in addition to being formed in the upper multilayer reflector 38.

  Similar to the annular groove 21 in the embodiment, the annular groove 21c is provided for forming the mesa post MP3, and is etched to a depth reaching the lower cladding layer 35, for example, as shown in FIG.

  An annular groove 22c is formed outside the annular groove 21c. Similar to the annular groove 22 in the first embodiment, the annular groove 22c is formed before forming the annular groove 21c forming the mesa post MP4, and has a cross section having a depth reaching at least the AlAs layer corresponding to the current confinement layer 38a. Have As in the first embodiment, after forming the annular groove 22c, an oxidation process is performed to form the current confinement layer 38a. Then, after forming the current confinement layer 38a, the annular groove 21c is formed, and the mesa post MP3 is formed. Note that the mesa post MP3 has a substantially truncated cone shape due to the influence of the etching process. Further, the annular groove 21c and the annular groove 22c have an annular shape centered on the substantially center of the current injection region 38c, for example, as in the case shown in FIG.

  As described above, according to the third embodiment, even when the substrate 32 made of n-GaAs is used, the mesa post MP3 is formed by performing the oxidation treatment after forming the annular groove 22c. Similar to the light emitting laser element, it is possible to realize a highly reliable surface emitting laser element in which damage to each layer due to oxidation treatment is reduced.

  In the surface-emitting laser element 31 shown in FIG. 6, the annular groove 22c has a depth reaching the upper layer of the lower multilayer reflector 33, but at least the upper multilayer reflector is formed to form the current confinement layer 38a. The depth reaching the AlAs layer corresponding to the current confinement layer 38a in the plate 38 is sufficient. For example, the depth of the annular groove 22 c may be made shallow enough to reach the upper cladding layer 37 located above the active layer 6. In this case, the annular groove 21c provided for forming the mesa post MP3 does not necessarily have to be etched to a depth at which the active layer 5 is divided. When the annular groove 22c has a depth reaching the upper clad layer 37, the end face of the active layer 6 is not exposed during the oxidation process, and damage to the active layer 6 due to the oxidation process is small. Therefore, even when the annular groove 21c is shallow enough to reach the upper cladding layer 37 on the active layer 6, the damaged region of each layer end face corresponding to the upper multilayer reflector 38 and the reflection of the upper multilayer film in the mesa post MP3. The mirror 38 can be isolated and the influence on the active layer 6 due to the volume change in the oxidation process can be reduced.

  Further, after performing the same process as the stacking process shown in FIG. 3A, an annular groove 22c is formed by performing a photolithography process and an etching process, and each process shown in FIGS. Similar processing is performed to manufacture the surface emitting laser element 31.

(Embodiment 4)
Next, a surface emitting laser element according to Embodiment 4 will be described. FIG. 7 is a cross-sectional view showing the configuration of the surface emitting laser element according to the fourth embodiment. As shown in FIG. 7, the surface emitting laser element 51 according to the fourth embodiment uses a substrate 52 that is a semi-insulating GaAs substrate.

  A current confinement layer 3 a is formed on the upper end layer of the lower multilayer-film reflective mirror 53 formed on the substrate 52. Of the lower multilayer reflector 53, a layer 53e having a layer in contact with the lower surface of the p-side electrode 61 and a layer closer to the active layer 6 than this layer is formed of a p-type semiconductor. On the other hand, in the lower multilayer film reflecting mirror 53, the layer 53f located on the substrate 52 side with respect to the layer in contact with the lower surface of the p-side electrode 61 is formed of a semiconductor not doped with impurities.

  A p-type electrode 61 is formed on the bottom of the annular groove 21d forming the mesa post MP4, and the n-side electrode 10 and the p-side electrode 61 are provided on the same surface side of the substrate 52. The annular groove 21d exposes the layer 53e formed of the p-type semiconductor in the lower multilayer reflector 53 in order to electrically connect the p-side electrode 61 and the layer 53e formed of the p-type semiconductor. Need to be deep.

  Similarly to the annular groove 22 in the first embodiment, the annular groove 22d provided outside the annular groove 21d and provided for forming the current confinement layer 3a is a semiconductor in which impurities in the lower multilayer reflector 53 are not doped. And has a depth reaching the layer 53f formed. This is because it is necessary to disconnect the electrical connection between the mesa post MP4 portion and the region outside the annular groove 22d. The mesa post MP4 has a substantially truncated cone shape due to the influence of the etching process.

  As described above, according to the fourth embodiment, the oxidation process is performed after the annular groove 22d is formed, and the mesa post MP4 is formed. Therefore, similarly to the surface emitting laser element according to the first embodiment, the oxidation process is performed. A highly reliable surface emitting laser element with reduced damage to each layer can be realized.

  Further, in the surface emitting laser element 51 according to the fourth embodiment, the entire lower multilayer film reflecting mirror 53 does not need to be conductive, and the lower multilayer film reflecting mirror 53 has a substrate that is closer to the contact layer with the p-side electrode 61. Since a semiconductor which is not doped with impurities can be used as the layer located on the side of 52, light loss can be reduced.

  In addition, after performing the process similar to the lamination | stacking process shown to FIGS. 3-1, the groove | channel 22d is formed by performing a photolithography process and an etching process, and it is the same as each process shown to FIGS. The surface emitting laser element 51 is manufactured by performing the above process and the process of forming the n-side electrode 10, the p-side electrode 61, and the electrode pad (not shown).

  In the fourth embodiment, the upper multilayer reflector 8 is also configured by laminating a semiconductor not doped with impurities or a dielectric such as SiOx or SiN, and the n-side electrode 10 is formed by the upper cladding layer 7. It is good also as a structure arrange | positioned on the top.

  The surface-emitting laser elements according to the first to fourth embodiments described above can also be applied to laser arrays in which surface-emitting laser elements are integrated in a one-dimensional or two-dimensional arrangement on the same substrate. In such a laser array, as the reliability of the laser array, reliability is required in all of the plurality of integrated surface emitting laser elements. Therefore, the application of the surface emitting laser element according to the present invention is effective.

1 is a cross-sectional view illustrating a configuration of a surface emitting laser element according to a first embodiment. It is a figure explaining the annular groove shown in FIG. It is a figure explaining the manufacturing method of the surface emitting laser element shown in FIG. It is a figure explaining the manufacturing method of the surface emitting laser element shown in FIG. It is a figure explaining the manufacturing method of the surface emitting laser element shown in FIG. It is a figure explaining the manufacturing method of the surface emitting laser element shown in FIG. It is a figure explaining the manufacturing method of the surface emitting laser element shown in FIG. It is a figure explaining the other example of the annular groove shown in FIG. It is a figure explaining the annular groove in Embodiment 2. FIG. It is sectional drawing which shows the structure of the surface emitting laser element concerning Embodiment 3. FIG. 6 is a cross-sectional view illustrating a configuration of a surface emitting laser element according to a fourth embodiment. It is sectional drawing which shows the structure of the conventional surface emitting laser element. It is a figure explaining the progress of oxidation in a multilayer-film reflective mirror. It is a figure explaining the dislocation which arose in the active region in the conventional surface emitting laser element. It is a figure explaining the dislocation area | region propagated to the active region in the conventional surface emitting laser element.

Explanation of symbols

1, 31, 51, 101 Surface emitting laser element 2, 32, 52, 102 Substrate 3, 33, 53, 103 Lower multilayer reflector 3a, 38a, 108a Current confinement layer 3b, 38b, 108b Oxidized region 3c, 38c, 108c Current injection region 3d AlAs layer 5, 35, 105 Lower cladding layer 6, 106 Active layer 7, 37, 107 Upper cladding layer 8, 38, 108 Upper multilayer reflector 9 Insulating layer 10, 41, 111 n-side electrode 11 , 40, 61, 110 p-side electrode 12, 112 electrode pad 21, 21a, 21c, 21d annular groove 22, 22a, 22c, 22d annular groove 22b hole 109 polyimide layer DL dislocation EA light emitting region L laser light MP1, MP3, MP4 , MP5 Mesa Post

Claims (14)

A substrate (2);
On the substrate (2) , a lower multilayer reflector (3), a lower cladding layer (5), an active layer (6) having a quantum well structure , an upper cladding layer (7), and an upper multilayer reflector A semiconductor stacked structure in which (8) are sequentially stacked;
In a surface emitting laser element having
A first groove (21) surrounding a light emitting region in the active layer (6);
A second groove (22) surrounding the first groove (21);
With
The first groove (21) forms a mesa post (MP1) including a stacked portion above the upper layer of the lower multilayer reflector (3),
A current having a current injection region (3c) on the central axis of the mesa post (MP1) in one of the upper end layer of the lower multilayer reflector (3) and the lower end layer of the upper multilayer reflector (8) A constriction layer (3a) is formed by oxidizing a part of the region by oxidation treatment from the side wall surface of the second groove (22),
A first electrode (10) having an opening at the center of the top surface of the mesa post (MP1) is formed on the upper multilayer reflector (8).
A surface emitting laser element characterized by the above. A second electrode is formed on the back surface of the substrate;
The first groove has a depth reaching the lower cladding layer;
The surface emitting laser element according to claim 1, wherein the second groove has a depth reaching the current confinement layer . A second electrode is formed at the bottom of the first groove;
The first groove has a depth that reaches a layer of the lower multilayer reflector that is electrically connected to the second electrode;
The surface emitting laser element according to claim 1, wherein the second groove is formed deeper than the first groove . The said 1st groove | channel (21) and the 2nd groove | channel (22) are the cyclic | annular groove | channels which make the concentric circle centering on the said light emission area | region in the said active layer (6). The surface emitting laser element according to any one of to 3 . The said 1st groove | channel (21) and the 2nd groove | channel (22) are the polygonal groove | channels which make the concentric shape centering | focusing on the said light emission area | region in the said active layer (6), It is characterized by the above-mentioned. Item 4. The surface emitting laser element according to any one of Items 1 to 3 . It said second groove (22), an annular first groove (21) and a plurality formed in a region which forms a concentric hole of claims 1-3, characterized in that it is composed of (22b) The surface emitting laser element according to any one of the above. The surface emitting laser element according to any one of claims 1 to 6 , wherein the lower multilayer mirror (3) and the upper multilayer mirror (8) include a semiconductor layer containing at least Al. . A substrate, and a semiconductor multilayer structure in which a lower multilayer reflector, a lower clad layer, an active layer of a quantum well structure, an upper clad layer, and an upper multilayer reflector are sequentially laminated on the substrate; A surface-emitting laser device in which a current confinement layer having a current injection region in a light emitting region in the active layer is formed on any one of an upper end layer of the lower multilayer reflector and a lower end layer of the upper multilayer reflector. In the manufacturing method,
Forming a second groove having a depth reaching at least the current confinement layer so as to surround the light emitting region in the active layer in the semiconductor multilayer structure;
Oxidizing a partial region of the semiconductor multilayer structure through the second trench to form the current confinement layer;
A first groove is formed inside the second groove so as to form a concentric circle centering on the light emitting region in the active layer with the second groove, and an upper end of the lower multilayer reflector Forming a mesa post including a laminate portion above the layer;
Forming a first electrode having an opening in the center of the upper surface of the mesa post on the upper multilayer reflector;
A method for manufacturing a surface-emitting laser element comprising: Further comprising forming a second electrode on the back surface of the substrate;
The first groove is formed to have a depth reaching the lower cladding layer,
The second groove is formed to have a depth reaching the current confinement layer.
The method of manufacturing a surface emitting laser element according to claim 8. Forming a second electrode at the bottom of the first groove;
The first groove is formed to have a depth reaching a layer electrically connected to the second electrode in the lower multilayer reflector.
The second groove is formed deeper than the first groove.
The method of manufacturing a surface emitting laser element according to claim 8. The said 1st groove | channel and the said 2nd groove | channel are formed in the cyclic | annular groove | channel which makes the concentric circle centering on the said light emission area | region in the said active layer, The any one of Claims 8-10 characterized by the above-mentioned. The manufacturing method of the surface emitting laser element as described in any one of. The said 1st groove | channel and the said 2nd groove | channel are formed in the polygonal groove | channel which makes the concentric shape centering on the said light emission area | region in the said active layer, The any one of Claims 8-10 characterized by the above-mentioned. The manufacturing method of the surface emitting laser element as described in one. The surface emitting laser according to any one of claims 8 to 10, wherein the second groove includes a plurality of holes formed in a region concentric with the annular first groove. Device manufacturing method. The surface emitting laser device according to any one of claims 8 to 13, wherein the lower multilayer mirror and the upper multilayer mirror are formed so as to include a semiconductor layer containing at least Al. Method.

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